Sounds like you have the skills to grow this up to 500 to 1k paying customers on your own. Early on you can increase ram/cpu to handle any initial scaling issues.
Once you even have 1k customers you'll have revenue to hire experts to help you with scaling and security.
"Scaling problems rule . . . "
http://www.youtube.com/watch?v=0CDXJ6bMkMY&t=23m34s
Sounds like you have the skills to grow this up to 500 to 1k paying customers on your own. Early on you can increase ram/cpu to handle any initial scaling issues.
Once you even have 1k customers you'll have revenue to hire experts to help you with scaling and security.
Good luck in 2015.